| | Accession Number | 5004725 |
| | Title | Use of Stable Isotopes to Determine the Relative Importance of Horseshoe Crab Eggs to |
| | Long-Distance Migrant Shorebirds in Delaware Bay |
| | Project Description | Food quality and food availability during stopover are important factors that ultimately define the |
| | migratory and often reproductive fitness of migratory birds. In Delaware Bay, eggs of the Atlantic |
| | horseshoe crab(Limulus polyphemus)have long been believed critical to the maintenance of |
| | long-distant migrant shorebird populations. The age-old spectacle of migrant shorebirds feating on |
| | crab eggs may be threatened by a recent increase in the harvest of horseshoe crabs for |
| | commercial fishing bait. To better understand the importance of horseshoe crab eggs in the diet of |
| | spring-migrant shorebirds,we propose to apply stable isotope methodology to fingerprint foods |
| | used by shorebirds during stopover and determine the relative importance of each in the diet. |
| | Based on procedures developed during a pilot study in FY2000, isotopic signatures of C and N |
| | (and possibly S) will be obtained for plasma and packed cell fractions of small (200ul) blood |
| | samples taken from live-trapped shorebirds. We will demonstrate blood fraction signature changes |
| | for red knots (Calidris canutus) and ruddy turnstones (Arenaria interpres) during May stopover and |
| | relate those changes to the signature values predicted directly from crab eggs and an inventory of |
| | other alternative foods available. In addition, field measurements will be compared to those |
| | obtained in a controlled pen feeding trial that will evaluate isotopic turnover rates and end point |
| | fractionation signature values of captive red knots held on a strict diet of crab eggs. Red knots and |
| | ruddy turnstones that were collected in May 2000 will be used to document isotopic signature of |
| | breast muscle, liver and fat. An effort will be made to inventory the lipid types in shorebird fat |
| | reserves and to fingerprint essential amino acids of other tissues that could possibly be traced |
| | directly to a crab egg diet. |
| | Keywords | delaware bay, horseshoe crab, red knot, ruddy turnstone, stable isotope, |
| | Principal | Michael Haramis, USGS Patuxent Wildlife Research Center: michael_haramis@usgs.gov; Mark |
| | Investigators | A Teece, Dept of Chemistry, SUNY-Syracuse: mteece@esf.edu; |
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